Window shutter units for installation on the outside of a building are known such as in U.S. Pat. No. 2,301,568 dated Nov. 10, 1942, inventor F. J. Moss entitled WINDOW SHUTTER.
In this patent the shutter panels are moved along tracks between an opened position at the side of a window and closed position in front of the window and are manipulated by means of cables extending through the building wall to be accessible inside the building. The window shutter of this patent is not designed to be used in cold weather since the bore made through the building wall to accommodate the actuating cables cannot be properly sealed against cold air entrance. Also, in this patent, the shutter panels are not heat insulating and no seals are provided to surround the window opening and contact the closed shutter panels in order to form a heat insulating air chamber in front of the window.
U.S. Pat. No. 4,267,666 dated May 19, 1981 entitled SHIELD FOR A WINDOW, inventor James D. Davidson, describes shutters which are slideable within the building wall in an interior space of the latter to take an opened position. It follows that the shutters, when in the latter position, cannot be used as decorative items for the window since they are hidden from view. However, the shutter panels are made of heat insulating panels and they are sealed against the outside weather when in closed position.